Methods and apparatus of charge-sharing locking with digital controlled oscillators

Abstract

An integrated circuit device includes a digitally controlled oscillator (DCO), two charge-sharing capacitors, two charge-sharing switches, two pre-charge switches, and two DACs. The DCO has a first inverter and a second inverter. A first charge-sharing capacitor has a first terminal coupled to an input terminal of the first inverter through a first charge-sharing switch. A first DAC has an output terminal coupled to the first terminal of the first charge-sharing capacitor through a first pre-charge switch. A second charge-sharing capacitor has a first terminal coupled to an input terminal or an output terminal of the second inverter through a second charge-sharing switch. A second DAC has an output terminal coupled to the first terminal of the second charge-sharing capacitor through a second pre-charge switch.

What is claimed is: 
     
       1. An integrated circuit (IC) device comprising:
 a ring based digitally controlled oscillator (DCO) having a first inverter and a second inverter; 
 a first branch-one charge-sharing switch and a second branch-one charge-sharing switch; 
 a branch-one charge-sharing capacitor having a first terminal coupled to an input terminal of the first inverter through the first branch-one charge-sharing switch and coupled to an input terminal or an output terminal of the second inverter through the second branch-one charge-sharing switch; 
 a branch-one pre-charge switch; and 
 a branch-one digital to analog converter (DAC) having an output terminal coupled to the first terminal of the branch-one charge-sharing capacitor through the branch-one pre-charge switch. 
 
     
     
       2. The IC device of  claim 1 , wherein the first terminal of the branch-one charge-sharing capacitor is coupled to the input terminal of the second inverter through the second branch-one charge-sharing switch. 
     
     
       3. The IC device of  claim 2 , wherein the first inverter has an output terminal that forms a circuit node with the input terminal of the second inverter. 
     
     
       4. The IC device of  claim 2 , wherein the ring based DCO further comprises a third inverter, and wherein the first inverter has an output terminal that is coupled to the input terminal of the second inverter through the third inverter. 
     
     
       5. The IC device of  claim 1 , wherein the first terminal of the branch-one charge-sharing capacitor is coupled to the output terminal of the second inverter through the second branch-one charge-sharing switch. 
     
     
       6. The IC device of  claim 5 , wherein:
 the first terminal of the branch-one charge-sharing capacitor is coupled to a first input terminal of the first inverter through the first branch-one charge-sharing switch; and 
 the output terminal of the second inverter is coupled to a second input terminal of the first inverter and forms a circuit node with the second input terminal of the first inverter. 
 
     
     
       7. The IC device of  claim 1 , wherein the first inverter and the second inverter are non-differential inverters. 
     
     
       8. The IC device of  claim 1 , wherein the first inverter and the second inverter are differential inverters. 
     
     
       9. The IC device of  claim 1 , wherein the first inverter and the second inverter are pseudo differential inverters. 
     
     
       10. The IC device of  claim 9 , wherein the ring based DCO further comprises a third inverter, and wherein the first inverter has an output terminal that is coupled to the input terminal of the second inverter through the third inverter. 
     
     
       11. An integrated circuit (IC) device comprising:
 a ring based digitally controlled oscillator (DCO) having a first inverter and a second inverter; 
 a first branch-one charge-sharing switch and a second branch-one charge-sharing switch; and 
 a branch-one charge-sharing capacitor having a first terminal coupled to a first input terminal of the first inverter through the first branch-one charge-sharing switch and coupled to an output terminal of the first inverter through the second branch-one charge-sharing switch, and wherein the branch-one charge-sharing capacitor has a second terminal connected to a ground. 
 
     
     
       12. The IC device of  claim 11 , wherein an output terminal of the second inverter is coupled to a second input terminal of the first inverter and forms a circuit node with the second input terminal of the first inverter. 
     
     
       13. The IC device of  claim 11 , further comprising:
 a branch-one pre-charge switch; and 
 a branch-one digital to analog converter (DAC) having an output terminal coupled to the first terminal of the branch-one charge-sharing capacitor through the branch-one pre-charge switch. 
 
     
     
       14. The IC device of  claim 11 , wherein the first inverter and the second inverter are non-differential inverters. 
     
     
       15. The IC device of  claim 11 , wherein the first inverter and the second inverter are differential inverters. 
     
     
       16. The IC device of  claim 11 , wherein the first inverter and the second inverter are pseudo differential inverters. 
     
     
       17. The IC device of  claim 11 , wherein the ring based DCO further comprises a third inverter, and wherein the output terminal of the first inverter is coupled to an input terminal of the second inverter through the third inverter. 
     
     
       18. An integrated circuit (IC) device comprising:
 a ring based digitally controlled oscillator (DCO) having a first inverter and a second inverter; 
 a first branch-one charge-sharing switch and a second branch-one charge-sharing switch; and 
 a branch-one charge-sharing capacitor having a first terminal coupled to a first input terminal of the first inverter through the first branch-one charge-sharing switch and coupled to an input terminal of the second inverter through the second branch-one charge-sharing switch, and wherein the branch-one charge-sharing capacitor has a second terminal connected to a ground. 
 
     
     
       19. The IC device of  claim 18 , wherein an output terminal of the second inverter is coupled to a second input terminal of the first inverter and forms a circuit node with the second input terminal of the first inverter. 
     
     
       20. The IC device of  claim 18 , further comprising:
 a branch-one pre-charge switch; and 
 a branch-one digital to analog converter (DAC) having an output terminal coupled to the first terminal of the branch-one charge-sharing capacitor through the branch-one pre-charge switch.